I too have been looking hard at this niche. UFC just signed a deal with ESPN where ESPN will finally be covering highlights of the sport. (Disney owns ESPN!) They also signed deals with HBO, bought Pride, and doing international shows now.
You know the niche is on fire when you go to Barnes and Noble and they have 5-6 different magazines on one niche.
As a marketer I look at the customer base and see a bunch of mostly young single men with big ego's...Sounds like buyer's to me!
I'd say you could easily start a membership site where you and a your BJJ instructor do a weekly series of videos teaching people how to get into the MMA sport, through in a forum, some affiliate ads and you got yourself a decent business.
P.S. I just saw that you are able to use
Google Site-Targeting to advertise right on front of Sherdog.com also! If I weren't so busy I'd be all over this like white on rice.